test dispatch queue, dispatch semaphore, ...

dispatch_queue_test.swift

import UIKit
import Foundation

let queue = DispatchQueue(label: "wotjd", attributes: .concurrent)

func sendMessage(str: String, pendingTime: UInt32, completion: @escaping () -> Void) {
    queue.async {
        sleep(pendingTime)
        print(str)
        completion()
    }
}

let pendingStart:DispatchSemaphore = DispatchSemaphore(value: 0)
let pendingUpload:DispatchSemaphore = DispatchSemaphore(value: 0)

let startUpload = DispatchWorkItem {
    sendMessage(str: "upload started!", pendingTime: 2) {
        print("started")
        pendingStart.signal()
    }
}

let uploadInfo = DispatchWorkItem {
    pendingStart.wait()
    sendMessage(str: "Info uploaded!", pendingTime: 1) {
        print("uploaded")
        pendingUpload.signal()
    }
}

var isRunning = true
let dataQueue = DispatchQueue(label: "wotjd_data")
var data = [Int]()

var valueSum = 0
var ESCounter = 0
let sendES = DispatchWorkItem {
    valueSum = 0
    dataQueue.sync() {
        if !data.isEmpty {
            for i in 0..<data.endIndex {//stride(from: endIndex - 1, through: 0, by: -1) {
                isRunning = data[i] != 499  // end loop trigger
                valueSum += data[i]
            }
            data.removeAll()
        }
    }
    if valueSum != 0 {
        pendingUpload.wait()
        sendMessage(str: "[ES:\(valueSum)] uploaded!", pendingTime: 1) {
            print("uploaded")
            ESCounter += 1
            pendingUpload.signal()
        }
    }
}

//queue.sync(execute: startUpload)
//queue.sync(execute: uploadInfo)
startUpload.perform()
uploadInfo.perform()

let jobQueue = DispatchQueue(label: "wotjd_job", attributes: .concurrent)
jobQueue.async {
    var a = 0;
    for value in 0..<500 {
        dataQueue.async() {
            data.append(value)
        }
        a += value
    }
    print("sum result = \(a)")
}

//sleep(1)
//sendES.perform()
while isRunning {
    sendES.perform()
}

var str = "Hello, playground"